Pneumatic applicators are often used in the seeding and fertilizing of agricultural fields. A pressurized hopper is filled with the seed or other particulate matter to be distributed. The hopper includes a metering device at its lower end for controlling the feeding of the particulate matter into a main conduit. The main conduit extends from the output of a centrifugal fan to a primary distribution manifold. Branch lines run from the primary distribution manifold to secondary distribution manifolds which, in turn, distribute the particulate matter over a predetermined area. The centrifugal fan creates an air stream to carry the particulate matter which enters the main conduit from the hopper through the metering device to the primary and secondary distribution manifolds in order to be distributed.
It has been found that in order to uniformly distribute particulate matter with a pneumatic applicator, it is necessary to achieve a uniform distribution of the particulate matter across the cross-section of the portion of the main conduit extending between the centrifugal fan and the primary distribution manifold. Typically, in prior pneumatic applications, the main conduit includes a horizontal section extending from the centrifugal fan and a vertical portion extending into the primary distribution manifold. The horizontal and vertical portions of the main conduit are interconnected by an elbow. During use, the particulate matter will tend to become concentrated within the rear of the elbow such that the distribution of particulate matter within the vertical portion of the main conduit is no longer uniform. This, in turn, results in the non-uniform distribution of the particulate matter by the pneumatic applicator.
Numerous approaches have been developed to improve the distribution of the particulate matter across this cross-section of the main conduit. By way of example, Kelm, U.S. Pat. No. 4,575,284 discloses a pneumatic applicator wherein a section of the main conduit includes inwardly directed, internal projections which urge the particulate matter toward the center of the main conduit. A conical forcing cone may be positioned on the output end of this section of the main conduit to gradually narrow the flow path and increase the velocity of the air stream into the distribution manifold.
However, as shown in the Kelm '284, prior forcing cones are of a uniform thickness. Due to such a construction, forcing cones tend to become damaged when interconnected to corresponding distribution manifolds. If a forcing cone is damaged such that the forcing cone is no longer symmetrical with respect to the longitudinal axis of the vertical portion of the main conduit, the flow of particulate matter into the distribution manifold will no longer be uniform. This, in turn, results in a non-uniform distribution of particulate matter by the pneumatic applicator. Consequently, while the pneumatic applicator disclosed in the Kelm '284 patent somewhat improves the uniformity of the distribution of the particulate matter, it is highly desirable to further improve the uniformity of the distribution of the particulate matter beyond that provided by the pneumatic applicator disclosed in the Kelm '284 patent.
Therefore, it is a primary object and feature of the present invention to provide a guide structure for facilitating the uniform distribution of seed and fertilizer with a pneumatic applicator.
It is a further object and feature of the present invention to provide a guide structure for a pneumatic applicator which is simple and inexpensive to manufacture.
It is a still further object and feature of the present invention to provide guide structure for a pneumatic applicator which is more durable than prior art guide structures.